US Army Corps of Engineers
Hydrologic Engineering Center

Mill Creek

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Mill Creek, Washington - Partnering to restore habitat and function

USACE’s Walla Walla District is engaging with the Sustainable Rivers Program to evaluate potential environmental opportunities at a diversion dam along Mill Creek in Walla Walla, Washington.

During high flow events, the main diversion dam at Mill Creek captures water and diverts it to an off-stream storage reservoir.
Mill Creek Main Diversion Dam - During high flow events, the main diversion dam at Mill Creek stores and diverts water to an off-stream reservoir (USACE photo).
This map shows the locations of the Mill Creek channel, main diversion dam, storage reservoir, and channel that returns water to Mill Creek.
Mill Creek Master Plan - This map shows the locations of the Mill Creek channel, main diversion dam, storage reservoir, and channel that returns water to Mill Creek.
Located just a few miles east of Walla Walla, Bennington Lake is an off-stream reservoir designed to store water during high-flow events on Mill Creek.
Bennington Lake - Located just a few miles east of Walla Walla, Bennington Lake is an off-stream reservoir designed to store water during high-flow events on Mill Creek (USACE photo).
During high water events on Mill Creek, two diversion dams capture water in the stream and divert it to Bennington Lake, an off-stream reservoir. This photo shows the area behind the diversion dams, known as the forebay, that were the focus for the Sustainable Rivers Program.
Mill Creek Diversion Dams - During high water events on Mill Creek, two diversion dams capture water in the stream and divert it to Bennington Lake, an off-stream reservoir. This photo shows the forebay above the diversion dams, which was the primary area for potential environmental benefits considered by Walla Walla District and partners with support from the Sustainable Rivers Program.
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Located about 3½ miles upstream from Walla Walla, Washington, Mill Creek Dam was built in the 1940s to reduce flood risk to the city. The project also provides outdoor recreation opportunities for the public.

U.S. Army Corps of Engineers (USACE) infrastructure at Mill Creek consists of an off-stream storage reservoir, Bennington Lake; a leveed channel upstream and downstream of Walla Walla; and two diversion dams on Mill Creek. During high water events, these diversion dams raise the water level so that floodwaters from Mill Creek can be diverted into a separate channel that leads to the off-stream reservoir.

In 2021, Walla Walla District and partners, with support from the Sustainable Rivers Program (SRP), evaluated opportunities for environmental improvements at the main diversion dam.   Read More

Partners
  • USACE Walla Walla District
  • Confederated Tribes of the Umatilla Indian Reservation
  • Mill Creek Work Group
  • Snake River Salmon Recovery Board
  • Tri-State Steelheaders
  • Washington Conservation Corps
  • Washington State Department of Ecology
  • Washington Department of Fish and Wildlife
  • Walla Walla 2020
  • Walla Walla Basin Watershed Council
  • Walla Walla County Conservation District
Resources
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